Hi thanks for your quick reply on my post, I have measured the tunnels and at there widest they are 40mm, could you recommend a make of prop I should be looking at, and would I need LH and RH props, will the motors u suggested be ok for a 12v system? I presume that's what voltage will be coming out of my esc's ( I have viper marine 20's) thanks again
15volt 545s will be fine on a 12volt system, since a fully charged 12v battery is 14 and a bit volts, and a Viper 20 is well capable of handling a 545. 35mm plastic props would be a good start. Once the system is settled and proved to work, you could go to a size bigger than the tunnel, and cut down the blades to fit, giving the more squared off, but still radiused, end. Plastic because they are generally cheaper than brass, and thus experimentation is less painful.
Counter rotating is good on a single hull with two props, probably doesn't make a blind bit of difference on a twin hull with the props in tunnels.
Replies are best on open forum rather than by PM, it everybody else a chance to contribute.
To aid cheap experimenting, below is a drawing of a blank for making a prop from sheet brass. Resize, print on paper, stick paper to sheet brass, drill hole in middle and size to suit propshaft, solder a brass nut over the hole, cut out the blades with snips, tidy with file, tweak blades for pitch. You now have a custom prop, variations are only limited by imagination and your abilities with a school compass.
